WAMS assisted frequency and voltage stability based adaptive load shedding scheme

A power system, operating close to its power transfer limit, may experience frequency as well as voltage instability on occurrence of a critical contingency. This paper proposes a two-step adaptive load shedding strategy, simultaneously addressing the frequency and the voltage instabilities through estimation of magnitude of the disturbance and evaluation of the stability margins. In the first step, disturbance power is calculated, assuming the availability of the real-time data from wide area measurement system (WAMS). This is compared with a threshold value of power mismatch, derived using a low order system frequency response (SFR) model, to judge the severity of the disturbance. Optimal locations and magnitude of the load curtailments have been decided according to a dynamic voltage stability index, computed at each load bus. The second step of the proposed scheme determines the optimal re-dispatching of generators to ensure minimal load curtailments for the post disturbance operating condition. Performance of the proposed scheme is tested on New England 39-bus system.